Doctor knives



Jan. 5, 1965 E. SMITH ETAL 3,163,878

DocToR KNIVES Filed neo. 4, 1962 I 5 sheets-sheet 1 INVENTORS En?. fnv/LL BY nana: .(afcr Jan. 5, 1965 E. sMlTH ETAL DOCTOR KNIVES 5 Sheets-Sheet 2 Filed Dec. 4, 1962 lv Qur and.

E. SMITH ETAL Jan. 5, 1965 DOCTOR KNIVES 5 Sheets-Sheet 5 Filed Deo. 4, 1962 INVENTOR eric In b BY Handi' mdf@ l l l l l I l I IIIIIIIIIIIIII S L@ .Qu

United States Patent O 3,163,878 DQTQR KNIVES Eric Smith, Bury, and 1lhoinas Scholes, Holcombe Broch, naar Bury, England, assigner-s Vto D. S. T. Pattern and Engineering Company Limited, a British company of Great Britain, Northern ireland, and the Isle of Man Fiied Dec. 4, 1962, Ser. No. 242,246 7 Claims. (Cl. 15-256.51)

This invention. relates to doctor knives, such as are used in connection with the roller or cylinder of a papermaking, bleaching, dyeing or printing machine.

A basic requirement of any doctor knife is that the pressure of the blade against the coacting roller or cylinder shall be as uniform as possible throughout its length, but it is believed that the doctor knife forming the subject of our prior Patent No. 2,914,788 was the iirst to achieve any satisfactory degree of uniformity of blade pressure when applied to rollers or cylinders of substantial length and/ or subjected to high temperatures such as voccur in papermaking machinery.

Under such conditions the previously known doctor knives proved unsatisfactory since their blades were adversely influenced by the inevitable sagging or distortion of their supporting means and were also unable sufficiently to accommodate themselves to the substantial non-cylindricality or camber which a long roller or cylinderwill often exhibit.

In the patented doctor knife aforesaid the blade or blade-assembly is mounted in a channel-like holder in such manner as to locate against the base of the channel and to bear upon a resilient fulcrum extending longitudinally of the latter near its mouth, the part of the blade or blade-assembly between such fulcrum and the j channel base being engaged between two opposed longitudinally-disposed abutments which hold the blade or blade-assembly clear of the channel walls and at least one of which is a tube iniiatable to urge the free edge of the blade against the associated roller or cylinder with an adjustable pressure distributed uniformly along its length. l

The resultant freedom of the blade to float within its holder renders it substantially unaffected by any sagging or distortion to which such holder is subject and enables very heavy cambers to be accommodated, while, if the three resilient members aforesaid (or at least the two abutments) consist of tubes, the optimum setting of the blade can quickly be obtained by adjustment of their respective inflation pressures.

However, the accommodation within it of two opposed inflatable tubes necessarily renders the channel-like holder ICCL side of said flange adjacent said roller or cylinder with capacity for localized iiexure and radial movement. A plurality of rocking levers, which may be identical to each other, are fulcrummed side-by-side upon said shaft and have corresponding arms cranked away from said rolleror cylinder so as to clear the free edgesof said flange. A doctor blade is detachably secured to the cranked ends of the several levers through the medium of a flexible backing plate secured to said ends. Inflatable tubes are interposed between said levers andsaid flangeat opposite sides of the said shaft.

In order that the present invention may be readily carried into effect, it will Vnow be described with reference to the accompanying drawings, wherein:

FIG. l is a fragmentary front elevation of one form of doctor knife embodying the present invention;

FIG. 2 is a section taken along the line 2 2 of FIG. l;

FiG. 3 is a detail view of a part of the embodimentof FIG. l;

FIG. 4 is a fragmentary end elevation of the embodimentof FIG. l;

FIG. 5 is a fragmentary section taken along the line S-S of FG. 4; and

FIG. 6 is a fragmentary plan view of the embodiment of FIG. l.

In the example illustrated, the rigid carrier portion of the doctor knife consists of a stout rolled-steel angle 1G somewhat longer than the roll, roller or cylinder 11 to be doctored and having welded to the outer side of one of its ianges -two square-section bars 12 whose projecting ends are turned to form aligned trunnions 13 whereby I the carrier is mounted in suitable brackets for oscillation about an axis parallel to that of the roll, 'roller or cylinder 11 and adjacent the'periphery of the said roll.

The other ange of the rolled-steel angle 10 extends towards such periphery and has screwed into it a row of small blocks 14 with aligned clearance holes 15 for a fulcrum shaft 16 of, for example, 7/6 inch diameter, which extends parallel to the axis ofthe trunnions 13 for the full length of the angle-section carrier 10.

Freely mounted on this shaft 16 area series of rocking f levers 17, a plurality of these such as, for example, six, being accommodated betweenV consecutive bearing blocks 14 with a minimum of clearance between their lateral faces. Each of such levers which may be about l inch s wide for the most part and each may have a'relatively of the patented doctor knife somewhat bulky in a direction perpendicular to the blade, and prolonged experience with such device in paper-making machinery has shown that, even when its free edge is faired by a spring plate bearing against the blade, the-upper part of the holder tends to hinder the passage Vof the paper or pulp removed by the blade and may lead to blockages between adjacent rollers or cylinders.

The object of the present inventionis to provide an alternative construction of doctor knife Ywhich is not subject to the above-mentioned drawback, while providing substantially the same uniformity of pressure along the length of the blade as the patented device, together with equivalent capacity for adjustment of the blade to an optimum position and for accommodation thereof to heavily cambered rollers or cylinders.

A doctor knife according to the present invention comprises a rigid carrier having a fiat ange directed towards.

thin portion through which the fulcrum shaft 16 passes, so that the presence of the bearing blocks 14 does not interferewith the uniform spacing of the levers 17 along such shaft. K s

The shaft 16, positioned endwise by collars 18, is mounted non-centrally with reference to the adjacent ange of the angle-section carrier 10, so that each lever 17, which extends the full width of such ange, has a short inner arm 19 and a long outer arrn 20. Inflatable tubes 21 and 22 of correspondingly different cross-sectional area are positioned between and engage the carrier flange aforesaid and coplanar at faces of the arms 19 and 20.

The two tubes, which maybe iniitally of-circular section of, for example, l-inch and 1% inchesV in diameter, respectively, are attened at opposite ends to enter elongated tapered holes in plates 23 supported upon the extremities of the fulcrurn shaft 16. Secured by screws 24 to the outer face 'of each end plate 23 are a pair of complementary tapered plugs 25 whereby the tubes are secured within the elongated holes aforesaid, two of these' plugs being drilled and tapped at 26 for connection by is cranked to provide a ilat terminal portion 27 which is Patented Jan. 5, 1965 spaced from such flange and is parallel to the surfaces engaged by the inflatable tubes 21 and 22;

A flexible metal plate 2S overhanging both forwardly and rearwardly as well as at the ends of the row of levers 17; isfsuitably. secured, such as by being riveted,

at 29. tothe severalat terminal portions of the levers. Y

The levers. 1T are. rebated at their front ends to accommodate a hard steel blade 30 between themselves. and the backing plate 28; projecting'y tabs 31 Von suchblade' engaging with locating recesses 32 in the rebated'parts of the leversl'. j

It will be.I appreciatedzthat the levers i7v form a series of supporting ngersfor the blade 30; which is thus able to, flex freely in a longitudinal direction while bearing against the roll, roller or cylinder 11. Y Y l The fulcrum shaft 16 islikewise free to flex, due to its small diameter and substantial: clearance in the bearing blocks 14, so that no appreciable sag or distortion can be transmitted thereto from the carrier angle 1G.

The varying angular positions of the several levers 17, which enable the edge of the blade 3d tocontact the roller or cylinder. 11` with uniform pressure throughout its length, are accommodated by the inflated tubes 21 and 22;.which. act in opposition to determine such pressure and the attitude of the blade with reference to the roller or cylinder. periphery.

It will be appreciated that by adjusting the intlation pressures in the. tubesll and 22rtheV optimum setting of the blade 30 is readily achieved.

The.y recommended, procedure is.. to inflate the smaller tube 21 to 3 or 4 lbs. per sq. Vinch and then set the Vcarrier'l so that there isa gap of approximately 1% inches between the edge of the. blade Slt and the surfacel of the roll, roller or cylinder 11. The pressure in the tube 21 is Vthen-released and the larger tube l22./ is inflated, up to a maximum of 12 lbs. per sq. inch until'the blade engages the surface aforesaid, the .carrier l being adjusted towards or away from the roller or cylinder until trial by means of' a suitable y'gauge 33 indicates. that the plane of thegblade 30 is inclined at 30-to 35 degrees to the tangent at the point of contact. Y

The clean. outer surface of theV blade-holder represented by the backing plate 28 ,otfersrnor obstruction to Y therpaper or pulp removed from the roll, roller or eylin` derA 11 bythe blade30fand the extension ofthe backing plate4 28; Sabove the carrier; ltl'ensures an easy passage for such` material.

If it should ybe desired to doctor the lower part of the rolLroller or cylinder ll'linstead of itsupper part as shown, the levers vil? may. be `mounted in an inverted position .with reference Vto= the carrier angle 1t)` andthetubes 21;v and 22 may bedisposed above said carrier.

Wegclaim:

1. Rol-lV doctor apparatus .adapted .to be used with. a. roll, said apparatus comprising, incombination, a substantially. rigid carrier having a ilange directed; towards the roll with which saidV apparatus is to be used; a shaft positioned substantially parallel" to the axis ofthe roll and secured to said flangel with capacity for localized, flexurc and radialV movement; a plurality kof identicalV rocking levers fulcr'ummedside-byside upon said shaft and having corresponding arms cranked'away from the roll so kas to clear the free edge of said ilange; a flexible plate secured to .the cranked ends of.; said leversaardoctorV blade detachably secured to saidfiexible plate and projecting beyond'the saidrflexible4 plate towards theroll;

Vand inflatable tubes interposed between'saidy levers and.

said flange at opposite sides of said shaft.v

2. Roll doctor apparatus adaptedto be used with a roll,y said' apparatus comprising, Vin combination, a substantially rigid carrier having'a ilangedirectedtowards the roll with which said apparatusis to be used;'a row with itsaxis substantially parallel to that yof the` roll; a

plurality of rocking levers fulcruinmed side-by-side upon said shaft and having corresponding arms cranked away from the roll so as to clear the free edge of said ange; a flexible plate secured .to the cranked ends of said levers; a doctor blade detachably secured to said flexible plate and projecting beyond the said flexible plate towards the roll; and inflatable tubes interposed between said levers and said ilange at opposite sides of said shaft.

3. Roll doctor apparatus adapted to be used with a roll, said apparatus comprising, in combination, a substantially rigid carrier having a llange directed towards the roll with which said apparatus is to be used; aA

row of bearing blocks affixed to. saidange; a shaft having radial clearance in said blocks and supportedthereby with its axis substantially parallel to that ofthe roll; a plurality of rocking levers fulcrummed upon saidshaft and having corresponding arms cranked away from the roll so as to clear the free edgetof said flange, a group ofk said levers being disposed betweenfeach of said bearing blocks and the next with minimal clearance between their lateral faces; a flexible plate secured to the crankedk ends of said levers; a doctor blade detachably secured to said flexible plate and projecting beyondithe' said flexible plate towards the'roll; and inflatable tubes interposed between said levers and said flange at opposite sides of said shaft.

shaft positioned substantially parallel to the axis of the Y roll and secured to said flange with capacity -for localizedllexure and radial movement; a plurality of rocking levers fulcrummed side-by-side upon said shaft and having corresponding arms cranked away from the roll so as to clear the free edge of said flange; a exible plate secured to the cranked kends of said levers and projecting beyond the' said levers towards the roll; a doctor blade detachably engaged between the ends of said levers and the part of said plate projecting beyond the said levers; and inatable tubes interposed between said levers and said ilange at opposite sidesof said shaft.

5. Roll doctor apparatus adapted to be used with'a roll, said apparatus comprising, in combination, a substantially rigid carrier having a flange directed towards the v-roll with which said apparatus is to be used;` a shaft positioned substantially parallelA to the axis of the roll and secured to said flange with capacity for localized llexure and radial movement; a plurality of rockingy levers fulcrummed side-by-side upon said shaft and having correspondingA arms cranked 'away from the roll so as to clearthe free edge of said ange; a flexible plate secured to the cranked ends of said levers andjprojecting beyond the said levers towards the roll, .the ends of saidlevers being rebated where overhung by said plate; a doctor blade inserted betweensaid ends of said levers and said plate; locating tabs projecting from said doctor blade'to engage recesses inV said rebated ends of said levers; and inatable tubes interposed between said levers and said. liangey atvopposite sidesof said shaft. v

6. Roll doctor: apparatus adapted to berusedwith a roll, said apparatus comprising, in combination, aV substantially rigidcarrier having a flangeV directed towards: the troll .with `which VsaidI apparatus is to be used; a

roll and secured to said flange with capacity for localized Y flexure and radial movement; a` plurality of rocking levers.

fulcrummed side-by-side upon saidshaft, that arm ofreach such lever which extends towards the roll being relatively long and cranked to bring` its Afree -end to. thel side of said ilange remote from. said shaft; aV flexible plate secured to thecranked ends of said levers; a doctor blade detachably secured to said llexible plate and projecting beyond the said ilcxibley platetowards the roll; and an inflatable tube interposed between the shorter' arms of said levers and said a'nge, andVv aflarger inflatable tube interposed between said flange and the cranked arms of said levers.

7. Roll doctor apparatus adapted to be used with a roll, said apparatus comprising, in combination, a substantially rigid carrier having a flange directed towards the roll with which said apparatus is to be used; a shaft positioned substantially parallel to the axis of the roll and secured to said flange with capacity for localized ilexure and radial movement; a plurality of rocking levers fulcrumined side-by-side upon said shaft and having corresponding arrns cranked away from the roll so as t0 clear `the free edge of said ange; a flexible plate secured to the cranked ends of said levers; a doctor blade detachably secured to said flexible plate and projecting beyond the said flexible plate towards the roll; inflatable tubes interposed between said levers and said ange at opposite sides of said shaft; tube plates having inwardly tapering holes to receive opposite ends of said tubes; and tapered plugs secured to said tube plates and engaged in said tube ends to secure said tube ends in said tube-plate holes, two of said plugs being drilled'for introduction of pressure fluid into said tubes.

No references cited.

WALTER A. SCHEEL, Primary Examiner.

CHARLES A. WLLMUTH, Examiner. 

1. ROLL DOCTOR APPARATUS ADAPTED TO BE USED WITH A ROLL, SAID APPARTUS COMPRISING, IN COMBINATION, A SUBSTANTIALLY RIGID CARRIER HAVING A FLANGE DIRECTED TOWARDS THE ROLL WITH WHICH SAID APPARATUS IS TO BE USED; A SHAFT POSITIONED SUBSTANTIALLY PARALLEL TO THE AXIS OF THE ROLL AND SECURED TO SAID FLANGE WITH CAPACITY FOR LOCALIZED FLEXURE AND RADIAL MOVEMENT; A PLURALTIY OF IDENTICAL ROCKING LEVERS FULCRUMMED SIDE-BY-SIDE UPOLN SAID SHAFT AND HAVING CORRESPONDING ARMS CRANKED AWAY FROM THE ROLL SO AS TO CLEAR THE FREE EDGE OF SAID FLANGE; A FLEXIBLE PLATE SECURD TO THE CRANKED ENDS OF SAID LEVERS; A DOCTOR BLADE DETACHABLY SECURED TO SAID FLEXIBLE PLATE AND PROJECTING BEYOND THE SAID FLEXIBLE PLATE TOWARDS THE ROLL; AND INFLATABLE TUBES INTERPOSED BETWEEN SAID LEVERS AND SAID FLANGE AT OPPOSITE SIDES OF SAID SHAFT. 